Standard +0.3 This is a standard connected particles problem with friction on a horizontal surface. While it requires setting up force equations and solving simultaneously, it follows a well-practiced template that A-level mechanics students drill extensively. The horizontal setup is simpler than inclined plane variants, and the question likely guides students through the steps, making it slightly easier than average.
15 In this question use \(g = 9.8 \mathrm {~ms} ^ { - 2 }\)
In this question use \(g = 9.8 \mathrm {~m} \mathrm {~s} ^ { - 2 }\)
Uses \(m = \frac{W}{g}\); PI by sight of AWRT 0.07
\(m = \frac{0.65}{9.8} = 0.066\)
M1
States or uses \(F = \mu R\); PI by sight of \(0.26\)
\(D - F = ma\); \(D - 0.26 = 0.066 \times 0.91\)
M1
Forms three-term equation using \(a=0.91\), their \(F\) and their \(m\)
\(D = 0.32\)
A1
Forms fully correct equation with all values substituted correctly; AWRT 0.32
## Question 15:
$F = \mu R = 0.4 \times 0.65 = 0.26$ | B1 | Uses $m = \frac{W}{g}$; PI by sight of AWRT 0.07
$m = \frac{0.65}{9.8} = 0.066$ | M1 | States or uses $F = \mu R$; PI by sight of $0.26$
$D - F = ma$; $D - 0.26 = 0.066 \times 0.91$ | M1 | Forms three-term equation using $a=0.91$, their $F$ and their $m$
$D = 0.32$ | A1 | Forms fully correct equation with all values substituted correctly; AWRT 0.32
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